The line comes from How I Met Your Mother, the American sitcom that ran from 2005 to 2014, where Neil Patrick Harris played the suit-obsessed Barney Stinson. Barney used legendary as his highest praise, often splitting the word to tease out the payoff, and the gag became one of the show's most quoted running jokes. Clips and GIFs of the pause spread across forums and social media long after episodes aired, turning the phrase into shorthand for anything worth celebrating. It remains popular because the setup is instantly recognisable even without seeing the scene.